Reference for Medical Students, by Medical Students

Life in the eFAST Lane: Extended Focused Assessment with Sonography for Trauma (Part 1)

The Case: There are just too many eFAST cases to choose from. Which one to tell you…? Should I tell you about my first eFAST patient, the supposed-to-be-simple-but-really-wasn’t, on-coumadin guy who laid out his motorcycle? What about the lady from the rollover down a twenty foot embankment? Or the teenager from a horseback riding accident? Should I tell you about the night I hung out in resuscitation and did an eFAST on every patient that came through? A night in December I like to think of as Ultrasound Christmas. A night when a trauma alert rolled in and before I knew what was happening, the resident put the ultrasound probe in my hand and said “Go for it!” Needless to say it was AWESOME! Like do-a-secret-happy-dance-in-the-hallway-afterwards kind of awesome. I’m definitely still lovin’ the ultrasound elective, especially since I’ve become competent at eFASTs.

So what’s an eFAST you ask? It’s simple, really. It’s a systematic ultrasound scan to check for pneumothorax and free fluid (usually blood) in the abdomen and chest. It’s quick, easy, and incredibly useful. You don’t have to be a genius for this stuff. And it’s an ultrasound scan, so it means fewer patients being radiated by CT scans. Remember? Radiation bad. No radiation good. If you’re going to spend time in the ED, you should learn the eFAST. End of story. Plus if trauma’s your scene, you’ll get close to some wicked traumas. So now that you’re convinced… just how do you do an eFAST?

What’s eFAST All About?

The eFAST is a fast (pun intended) and easy way to check for blood in the chest and abdomen. eFAST is an acronym for extended Focused Abdominal Scan for Trauma. It’s an ultrasound exam designed for trauma patients that can be used at the bedside without interrupting ongoing care. Unstable patients with positive eFAST scans can then receive definitive care (get a chest tube, go to surgery, etc.) without the delay of waiting for a CT. The exam is a set of scans that quickly visualize free fluid (like blood) in the anatomical sites it most commonly collects, so the trick to quickly interpreting an eFAST exam is learning just where free fluid tends to collect. An eFAST looks at the right upper quadrant (RUQ), left upper quadrant (LUQ), pelvis, heart, and lungs. (Lungs are the extended part of the exam. Without the lung component it’s just called a FAST exam.) So that’s five ultrasound views, six if you’re picky about the whole 2 lungs thing, and you’ve completed an eFAST exam. It takes less than 5 minutes to complete, but more like 2 minutes as you approach ultrasound rock star status. Plus it’s more sensitive than x-ray for conditions like pneumo or hemothorax. Basically, eFASTs are a great ultrasound scan for rapidly identifying bleeding and other common injuries in the trauma patient.

The Patient: Who Gets an eFAST?

Blunt and penetrating abdominal trauma

Blunt and penetrating chest trauma

Ectopic Pregnancies

Suspected abdominal or thoracic free fluid or active bleeding

How Do I perform an eFAST?

Ultrasound Terms

You need to know a few fancy words because this is medicine and that’s what we do. Get used to it:­

Hyperechoic: when an image is brighter than surrounding tissue (due to greater reflection of sound).

Hypoechoic: when an image is darker than surrounding tissue (due to less reflection sound).

Note the marker on the probe. It corresponds to the marker on the ultrasound screen. ­ This helps you orient what you’re seeing on the screen with the probe position. ­

Marker position is important for proper scanning technique – traditional marker orientation is always either towards the patient’s head or the patient’s right side.

Structures at the top of the screen are closer to the probe than images at the bottom of the screen

As noted above, free fluid is anechoic. The presence of free fluid = positive eFast. Morrison’s pouch is the first place fluid typically collects in the upper abdomen; the pelvis is the first place you’re likely to see fluid in the lower abdomen.

Bone blocks sound wave transmission (and since ultrasound is based on sound waves… you get the picture). Rib shadowing may block your image, so you may have to move the probe around to find a good viewing window. That’s normal.

If you have difficulty finding a good image on the RUQ/LUQ views, turn the probe obliquely to see between the ribs.

Scanning Techniques

Heart

Probe position: Subxyphoid View

Probe marker: towards patient’s right

Place the probe just inferior to the xyphoid (…duh)

You may need to shift just right of the xyphoid to get a good image of the heart because the liver is your acoustic viewing window and it may not extend across to the middle or left

­ Now take your probe handle and lay it flat against the abdominal wall

Your probe is now pointing towards the patient’s head

It’s going to feel like you’re pinching the probe between your fingers and a bit like holding a pencil

The image:

You should be looking at the heart, obviously, but you’re seeing it through the liver

The right ventricle and atrium are towards the top of the screen (immediately next to the liver) with the pericardium represented as the single thin hyperechoic (white) line around the heart

Interpretation:

A positive exam has free fluid

Here you’re looking for free fluid in the pericardium, also known as a pericardial effusion

It will look like a black stripe between the heart and the pericardium

The fluid will collect in the pericardium nearest the liver (by the right ventricle) and potentially wrap around the apex of the heart

Don’t be fooled by epicardial fat pads. They’re in the pericardial space and can be dark, but not as dark as fluid. So if it’s not jet black, it’s probably just epicardial fat. Also, the heart will move “with” an epicardial fat pad but will move “within” a pericardial effusion.

Look at the heart’s global function. Is it moving? Is the right atrium or ventricle collapsed? Does it look like the heart is being crushed by an effusion?

Percardial tamponade, when fluid around the heart prevents the heart from expanding/filling, is a medical emergency! Take a second to fix the code brown that just happened in your pants. And do something! Now!

The heart of an eFAST is anatomy. Obviously, knowing your anatomy and the relationship between structures is important to an eFAST. If you can’t find a kidney, you’re out of luck (and unless you’re my mom, I’m not sure why you’re reading this anyways). But the real magic of anatomy is that it allows us to know where blood will collect first. Thanks to fascia and other physical structures free fluid consistently flows to the same places, making it possible for us to identify free fluid from thoracic and abdominal bleeding with only a few ultrasound views.

Gravity is another important factor here. Free fluid flows to the most dependent area (that means the lowest point) of an anatomic compartment as a result of gravity. So physical barriers create anatomic compartments (like the pericardium around the heart or the peritoneum in the abdomen) that limits where a fluid can travel AND gravity forces the fluid to accumulate in the most dependent areas. After that, there’s potential spaces to consider. Normally these are low volume spaces, but can expand to large volumes if occupied by fluid (like blood) or air. If you can visualize free fluid in a potential space, there’s probably badness going on. Basically, the anatomy allows us to determine where free fluid should collect and visualize that free fluid quickly using ultrasound. This is the basis of an eFAST exam. Now let’s talk specifics…

The heart scan is a quick and dirty scan. You’re just looking for free fluid in the pericardium and checking for cardiac tamponade. The pericardium is a fibrous sac surrounding the heart, which has little stretch to it. When an injury bleeds into the pericardium, increased pressure squeezes the heart. If that pressure exceeds right chamber pressures, the heart chambers can collapse and prevent both cardiac filling and output. This is bad, bad, bad! This is the code brown situation I was talking about earlier.

Thankfully, the subxyphoid view of the heart not only visualizes the pericardium, but also visualizes the right atrium and ventricle. This lets you assess if there is any atrial or ventricular collapse. Another point to note for this scan is that you’re using the liver as an acoustic window. Sound travels well through the liver, so it gives you a much clearer image if you use the liver to look at the heart. If you’re having trouble getting an image, remember to shift a little right (that’s patient right) of the xyphoid to better use the liver. The liver’s other role is as a landmark. The most dependent point in the pericardium is against the diaphragm, right next to the liver. This is the first place you’ll see fluid in the pericardial sac.

Figure 11 – Cardiac Anatomy in the subxyphoid view

The RUQ view visualizes the most dependent area in the supine patient, Morrison’s pouch. It’s the potential space between the liver and the right kidney. Because of its ability to expand and extreme dependence (low position) Morrison’s pouch is one of the first areas that intra-abdominal free fluid flows in a supine patient. Even fluid from the LUQ tends to flow here before it collects in the LUQ. Fluid can also collect between the liver and diaphragm, so remember to check there too.

The LUQ view visualizes the spleen and left kidney. Since the left kidney is higher than the right, move your probe a little superior when shifting from RUQ to LUQ scan. The spleenorenal recess (spleen-kidney interface) is a potential space, so examine it for free fluid. It is not nearly as dependent as Morrison’s pouch, so fluid will collect in other places in the RUQ too. Be sure to check the liver-diaphragm interface and the upper and lower portions of the spleen before you move on.

Both the RUQ and LUQ views visualize above the diaphragm. This is important because just above the diaphragm is an important dependent area of the lungs. If you’re going to see free fluid in the lungs, you’ll probably see it here. If there is free fluid above the diaphragm, think hemothorax or pleural effusion.